Workers who are obligated to work in high places such as on scaffolding, window ledges, and the like typically wear a body harness and/or a safety belt which is secured by a lanyard to some type of available anchorage. In the event the worker falls from a relatively high perch, he or she can reach a very high velocity in a matter of seconds. Depending upon the length of the lanyard, a falling worker's descent can be abruptly terminated causing serious bodily harm to the worker. Various shock absorbing devices have been developed over the years to decelerate a worker's fall, and thus cushion the resulting impact shock. The shock absorber is typically made part of the lanyard connecting the worker's body harness or belt to an anchorage. One prevalent type of shock absorber is disclosed in U.S. Pat. No. 3,444,957 to Ervin, Jr. that involves a length of high strength webbing that is folded over itself a number of times with the adjacent folds being stitched together. The stitching is adapted to tear apart when placed under a given dynamic load to absorb the energy generated by the fall. This type of absorber is relatively lightweight, compact, and thus easily portable as well as being easily retrofitted into existing safety systems. This type of shock absorber will herein be referred to as a tear away type of energy absorber.
An American National Standard Z359 relating to personal fall arrest systems was issued in 1992 and revised in 1999. The standard addressed different safety systems and various methods for arresting falls of workers from high places. The American National Standard is consistent in the most important features with the standards of other countries including those of the Canadian Standard CAN/CSA Z259.11-05. Most, if not all, tear away absorbers in present day usage cannot consistently pass the dynamic drop test set out in the United States National Standard.